The Transportation of Carbon Dioxide by Paraffine Oil and Some Other Substances.

Abstract

In a previous paper 1 the use of luminous bacteria as an oxygen indicator was described. Some rough estimates of the passage of oxygen through a number of substances were given, as determined by the length of luminescent columns of bacteria. The properties of several of these substances, notably dry collodion, were of interest and these and some others were selected for further study with reference to carbon dioxide. In this case the time in hours required for one atmosphere of carbon dioxide to decolorize 1 cm. of phenolphthalein in NaOH agar is used for comparison. It is clearly recognized that this is not a quantitative method for the study of diffusion as there is a concentration gradient of carbon dioxide in the colorless portion of the phenolphthalein as well as through the membrane closing the tube. Nevertheless, it makes a very striking demonstration for class use and does give a qualitative expression for the passage of carbon dioxide. The proper methods of quantitative study may be found in the papers of Krogh 2 and of Northrop, 3 to mention only two.

In the earlier experiment temperature control was relied on to minimize convection currents, since the experiments could run for only a short time. With the phenolphthalein, NaOH, agar system the agar was used to prevent convection currents in the solution into which the carbon dioxide diffused, but it at once became evident that convection currents in the lighter oils were assisting in the transportation of carbon dioxide, and a method was sought for reducing or eliminating them. The most efficient found was that of cutting disks of blotting paper which exactly fitted the inside of the test tubes used, saturating these with paraffine oil, and packing them tightly in the tube to the required depth. An easier method and one almost as efficient was that of saturating cotton with oil and packing it in the tube.